Organic light emitting diodes (OLEDs) have the potential of being used in solid state lighting to replace conventional light sources such as incandescent light sources. The traditional light sources have efficiencies lower than 15 lm/W, where OLED have the potential of reaching 100 lm/W. Potential uses for OLEDs include lighting products, backlights for LCD panels, and flat panel displays.
A typical OLED device structure is shown in FIG. 1. The device has multilayer organic films sandwiched between a metal cathode 10 and an indium tin oxide transparent electrode 20. Typically, a hole transporting layer 11 is deposited on the top of an ITO electrode 20 followed by the deposition of an emitting layer 12. Additional layers are sometimes added to the device structure to enhance the performance. One of the issues with OLEDs is that about 80% of the light generated by the device is trapped within the glass substrate 1 and only about 20% of the light can get out.